13-S-9: SKIDDER ROLLS OVER TIMBER CUTTER’S HEAD

On a mild, clear, and sunny day in the South, a skidder operator was pulling a drag of poplar logs with a cable skidder. The skidder had just crossed the bridge mats and started up a steep hill when the drive shaft came out. He and the timber cutter tried to fix the problem. They removed the belly pan and found that all but two of the bolts from the U joint yoke to the rear end were out. Since the skidder driver could not reach the last two bolts, he asked the timber cutter to see if he could reach them.

PERSONAL CHARACTERISTICS:

The skidder operator and 49-year-old timber cutter were considered fully trained for their primary jobs. However, neither individual had ever repaired a broken drive shaft on a skidder. They wore all required safety equipment, and they lowered the skidder blade and applied the parking brake.

UNSAFE ACTS & CONDITIONS:

The crew began working on the skidder while it was on a slope and furthermore did not chock the wheels. The timber cutter went to work under the skidder while its stability was in question. They undertook maintenance without understanding the operating systems.

ACCIDENT:

As the timber cutter removed the last bolt, the bolt broke and the skidder started rolling back down the hill. It rolled about four feet before stopping against the log pile to which it was hooked. The right front skidder tire rolled partially onto the cutter’s head and left shoulder, pinning him to the ground. The skidder driver removed the mud and dirt from the cutter’s mouth so he could breathe.

After the accident, the skidder driver spoke with a mechanic and learned that the bolts that hold the yoke to the rear end also thread into a disc for the brake system. Once the last bolt was taken out, it released the brakes.

INJURY:

The timber cutter suffered a severe contusion to the head as well as several fractured bones in his face and eye socket. He also suffered a broken rib. Had the ground not been soft and muddy, the result would have been a fatality. He was expected to miss about four months of work during his recovery period.

RECOMMENDATIONS FOR CORRECTION:

Tow or push equipment to level ground before performing maintenance.

Use a qualified mechanic to perform maintenance. Do not work on equipment if you do not know the system.

Lockout requires all forms of energy to be zeroed. Block or chock the wheels to prevent movement before placing yourself under a machine.